Thomas e



Rei ssnied 0a. 10, 1922.

Re.15,466 p UNITED STATES PATENT OFFICE.

THOMAS E. MURRAY, J 11., OF BROOKLYN, NEW YORK.

METHOD OF ELECTRIC WELDING.

in Drawing. Original 1m. 1,281,636 and 1,281,637, dated umber 15,1915,Serial 1m. 215,710 and 215,711, filed February 6, 1918. Application forreissueflled January 16, 1922. Serial No. 529,783.

To all whom it may cancer-n:

Be it known that I, THOMAS E. MURRAY, J r., a citizen of the UnitedStates,residing at Brooklyn, New York,.have invented a certain new anduseful Improvement in Methods of Electric \Velding, of which thefollowing is a specification.

The invention is an improvement in the art of electricwelding, whereby aweld can be secured of a strength equal to that of the metal welded, anda single, integral homegeneous body may be formed, and this can be onecontinuously over a contactarea of considerable extent with greatuniformity and great econom of time and labor.

As common y practised, electric welding is a sticking together of theopposing bodies by rendering their surfaces plastic or pasty and ressingthem into more or less close contact. fhe result is attraction betweenthe molecules at the surfaces of the respective bodies, caused first byrendering-said molecules mobile by heat, and then moving them by thepressure into closer proximity and sointo their fields of mutualattraction. In old physical nomenclature, the surfaces are then said toadhere.

While temperature of a degree suflicient to make the opposing surfacesadhesive will effect a union, the strength of said union is a todestruction; nor from the tests of one joint can the strength of otherjoints certainly be, inferred. A given joint may be amply strong to meetconditions involving small strain, as, for example, the uniting ofelectrical line conductors or the parts of' utensils or lightstructures, but it may be wholly inade uate to withstand the demands ofheavy loa s or shocks orof moving machinery.

The effort to make stronger joints has led to moderately increasingcurrent strength, or both current strength and current duration, for thepurpose of obtaining greater plasticity or fluidity of the metal; butthis leads primarily to burning of the metal. Increase of pressure leadsto greater extrusion of metal at the joint which is intensified when thefluidity or plasticity of the metal is augmented. The result. is thenmerely surface adhesion; as lJHfQlTP- OVHI a larger area. To

increase the duration of the current deteriorallps the physicalcondition of the metal it- I Another cause of uncertainty andunreliability of the welded joint is the great dif-v ficulty, and oftenpractical impossibility, of insuring a uniform current flow per unitarea of welding surface. If other materials are present in the metal,especially substances --of lower conductibilty, the current will causeunequal heating of the surface, with a result that one part may beburned before a proper plastic condition is produced elsewhere. So alsoif the surfaces exhibit protuberances which may contact before the moredepressed portions, the current may burn or the protuberances before thelastnamed portions are suitably heated, or even 1f the opposed surfacesare not rigorously parallel, the current will become concen trated andso affect the portions of said surfaces which first make contact.Increasing the current to obtain greater plasticity or' continuing itfor longer periods, or using greater mechanical pressure does not over-7 come these difficulties .I have discovered after much study andresearch, that I can produce' an electrically welded union possessing astrength as great as that of an integral mass of the same ma terial oflike cross-sectional area by subjecting the bodies to be welded to anelectric current of extremely and'abnormally high ampere strengthexisting for a 'very'brief period of time. t

' When the area is small, say about five square inches or under, Iprefer to use cur rents of about one hundred thousand amperesto thesquare inch When the area is large, say about twenty square inches orabove, I prefer to use currents .of about fifty 9 square inches in lessthan three-seconds. I

am actually welding two pieces ofsteel having an area of five squareinches in less than one-half a second; two pieces of steel having athickness of .109 inches and a length of eightydive inches in less thantwo seconds;

two pieces of steel having a. thickness of onesixteenth of an inch and atotal length of threehundred and fifty inches in less than threeseconds. In each of these cases I am using a current of extremely andabnormally high ampere strength existing for a very brief period oftime.

The operation is so rapid that it is impossible to becertain of thestages through which the work passes. I can state nth certainty only themethods used and, the re,.

sults achieved. My theory is as follows:

The weld is not caused by surface mole;- ular attraction or adhesion butby a complete dissociation of the molecules for a oertain distanceinward from the surface of eaclr body, followed by the intermingling ofthe molecules ofone body with those of the other, and their mutualattraction developed within the momentarily gaseous film. so that thesaid molecules become united throughout the mass. .Under the oldphysical nomenclature, theyv cohere It'- the two bodies are of the samematerial, then, after welding there is no solution of contr.

nuity, and the two bodiessimply become integrally one body' If the twobodies are of di'fiierent materials then while there is still nosolution of continuity, a portion of the welded massis compositeandpartakes'.

of the nature of'both bodies; that is to say,

if, for example, copper and zinc be the materials a portion of thewelded mass will be an alloy or mixture of the two metals.

The enormousl f high temperature developed, gasifiest e metal or metalsof the bodies instantly, and in the brief time period.

permits the molecules "to interminglej and cohere. With such amperestrengths there is no time for any burning of the metal or for theconduction of heat away throughthe-mass before the gasificationrof themetal and the inter-mingling of molecules occurs.

()1? course, the temperature. is far above that which would, permit themetal to become plastic or pasty. Because there is complete cohesion ofthemolecules within the mass the physical condition of the metal. is thesame at the place of union asanywhere else. Therefore the same strengtheverywhere follows as a necessary consequence. This can be accomplishedin no other way, so tar as I know. d

When currents of such extreme ampere trode in contact- With all foursides.

ess to use a high voltage.

and naturally so since the intermingling produced isot gases in whichthe molecules are free and comparatively widely separated. So also thereappears to be no limitation of surface areas which can be united. With asuitably strong momentary current it is as easy to weld areas of saytwenty square inches as areas of one square inch.

Another advantageous result attending my use of enormously strongcurrentis lhe neutralization of the dillicultiesdue to radiation from theheated bodies to the holding electrodes when the area of contact betweensaid bodies and said. electrodes is largely increased; To take a simpleillustration: Assume that two bars m easuri'ng incross sectional areaone square inch, are to be united. The best conditions are attained wheneach bar is inclosed, in a copper elec Iic'ach electrode is one inch inwidth, then the 'cont aot area of each electrode with its bar is foursquare inches. As already pointed out, I; can buttrweld. these bars bymy process and be certain that the strength at the union Will be equalto thatof the integral met-a1. Suppose,- however, while keeping the areathe same, the l form of that area be changed as, to illustrate, let thesurface area instead of one square inch in thesha peofa greater. This isincreased radiation surface of the bar, and, therefore the heatdeveloped will escape to the electrode niore rapidly than before. Thisloss 'i-s,as l-have' stated easily counteracted byan increasein theampere strength of the current. I It 'a current of given high amperestrength will produce a perfect union when. thegcontact area is a squareor other regular figure of uniform dimensions. the same result may beobtained when the figure is changed to one in which the dimensionswidely differ by increasing the current strength. All that is necessaryfor a given shape is to go on increasing the current strength until theperfect union is produced. After that, with unchanged conditions as toshape, material,-

etc, the welding'ot like bodies-may be. repeated. indefinitely.

Practical applications to the invention to these long narrow joints areindicated in specific cases referred to above.

lt is unnecessary in carrying out my procl have made good welds usingabout eight volts on the secondary ol a transformer.

' above.

This invention is to be distinguished from the method knownas"percussive Welding and from similar processes in which, by means ofan uncontrolled condenser discharge a considerable current is passed inan instant through small points or spots of contact such as the ends ofwires or rods or the socalled spot welding in which considerable areasare in contact but the welding is effected at separated points in thecontact area. My invention is useful in welding considerable areas ofcontactand making a continuous weld'over such areas by passing thecurrent through substantially the entire area of the contact, thecurrent being proportioned to such area. Examples of the considerableareas to which my invention is applied in this way. are recited Also myprocess is distinguished in that it uses a steady current (that is, ofsteady amperage) throughout the period of application, the amperage atthe end of the eriod being nearly equal to the average. 11 thepercussive methods referred to, the condenser discharge produces a highvoltage and a comparatively low amperage which tapers off gradually tozero. And where the time interval'is practically uncontrolled in V thesaid methods, with my method it varies inversely or in the oppositedirection from the variation in current'density, as indicated in theexamples given above.

Though I have described with great particularity of detail certainembodiments of my invention yet it is not to understood therefromthatthe. invention is restricted to the particular embodimentsdescribed. Various modificatibns thereof may be made by those. skilledin the art without departure from. the invention as defined in thefollowing claims.

1; The improvement in the art of electric welding, which consists insubjecting the bodies to be united to, a current of extremely highampere strength and of very brief duration. whereby said bodiesare-caused to form a single homogeneous body without solution ofcontinuity.

2. The improvement in the art of electric welding, which consists insubjecting the bodies to be united to a current of extremely high amperestrength and of very brief duration, and thereby producing moleculardissociation at each of the opposing faces of.

said bodies and an intermingling of the dissociated molecules, wherebysaid bodies are caused to form a single homogeneous body withoutsolution of continuity.

3. The improvement in the art of electric welding, which consists insubjecting two bodies of respectively different metals to a current ofextremely high ampere strength and very brief duration. and thereby probrief predetermined and regulated period of time as distinguished from asudden uncontrolled discharge.

5. The improvement in the art of electric welding, which consists insubjecting two bodies of respectively different metals to a current ofextremely high ampere strength applied for a very brief predeterminedand regulated period of time (as distinguished from a sudden anduncontrolled discharge).

6. The improvement in the artof electric Welding, which consists inbringinginto contact and under pressure considerable surfaces of thebodies to beunited, the area of the contact surfaces having a length substantially greater than its width, and passing through substantially theentire surface in contact a current of extremely high ampere strengthper unit of area of the contact surfaces and of very brief duration.

7. The improvement in the art of electric welding, which consists inbringing into contact and under pressure considerable surfaces of thebodies to be united, the area of the contact surfaces having a lengthsubstantially greater than its width, and passing through such bodies acurrent of extremely high ampere strength per unit of areaof the contactsurfaces, and of ye brief duration, the said ampere strength beinggreater than the ampere strength necessary to accomplish the same resultin Welding two bodies of identical material whereof the length of thecontact area is equal to the width. thereof.

8. The method of electrically welding. bodies 'whereof the contact areais one in which the length is greater than the Width, which consists insubjecting said bodies to a current of extremely high ampere strength.

tact and under pressure considerable areas of the bodies to be unitedand passing through substantially the entire area in contact a currentof extremely high ampere strength per unit of area of the contactsurfaces and of very brief duration.

10. The improvement in the art of electric welding, which consists insubjecting the bodies to be united to a current of extremely high amperestrength and of very brief duration, maintaining the high amperagethroughout the period of application of the current.

11. The improvement in'the art of electric welding which consists inbringing into contact and under pressure considerable areas of twobodies of respectively different metals and passing throughsubstantially the entire areas in contact a currentof extremely highampere strength per unit of areaof the contact surfaces and of Verybriefduration.

12. The improvement in the art of electric welding, which consists insubjecting the bodies to be united to a current of extremely high amperestrength in proportion to the contact area and of a very brief durationvarying in an inverse proportion to the cur-,

iny name.

THOMAS E. MURRAY, JR.

